Learning Unix for OS X Mountain Lion ppt

13 Launching the Terminal 13 Syntax of a Unix Command 14 Exercise: Entering a Few Commands 16 Types of Commands 17 Changing the Terminal’s Preferences 18 Features of the Terminal 22 Cust

Dave Taylor

Learning Unix for OS X

Mountain Lion

ISBN: 978-1-449-33231-0

[LSI]

Learning Unix for OS X Mountain Lion

by Dave Taylor

Copyright © 2012 Dave Taylor All rights reserved.

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Table of Contents

Preface ix

1 Why Use Unix? 1

The Power of Unix 1

Batch Renames and Extracting File Lists 4

Finding Hidden Files 5

Folders or Directories? 6

Thousands of Free Applications 7

Power Internet Connections 7

Commands Included with Unix 8

Displaying All Unix Commands 9

The 10 Most Common Unix Commands 9

A Simple Guided (Unix) Tour 10

2 Using the Terminal 13

Launching the Terminal 13

Syntax of a Unix Command 14

Exercise: Entering a Few Commands 16

Types of Commands 17

Changing the Terminal’s Preferences 18

Features of the Terminal 22

Customizing Your Terminal Session 23

Setting the Terminal’s Title 23

Using AppleScript to Manipulate the Terminal 24

Working with terminal Files 25

Working with the Terminal 25

The Shell Prompt 27

Entering a Command 27

Recalling Previous Commands 28

Completing File and Directory Names 29

iii

Running Multiple Commands on the Command Line 30

Correcting a Command 30

Ending Your Session 31

Problem Checklist 31

Customizing the Shell Environment 32

Picking a Login Shell 32

Changing the Command Prompt 33

Advanced Shell Customization 35

Shell Configuration Settings 35

Creating Aliases 38

The Unresponsive Terminal 39

3 Exploring the Filesystem 41

The OS X Filesystem 41

Your Home Directory 42

Your Working Directory 42

The Directory Tree 43

Absolute Pathnames 44

Relative Pathnames 45

Changing Your Working Directory 47

Files in the Directory Tree 49

Listing Files and Directories 51

The All-Powerful ls Command 51

Trying Out the ls Command 52

Using the -l Option 55

File Permissions 56

Calculating File Size and Disk Space 59

Calculating Available Disk Space 62

Exercise: Exploring the Filesystem 63

Protecting and Sharing Files 64

File Access Permissions 66

Setting Permissions with chmod 67

Changing the Group and Owner 70

Changing Your Password 71

Superuser Privileges with sudo 72

Exploring External Volumes 74

4 File Management 77

File and Directory Names 77

File and Directory Wildcards 80

Looking Inside Files 82

cat 82

iv | Table of Contents

less 83

grep 85

Creating and Editing Files 86

Text Editors and Word Processors 87

The vi Text Editor 89

vi Basics 90

A Simpler vi Alternative: Pico 96

The More Complex Option: Emacs 97

Managing Files 98

Creating Directories with mkdir 99

Copying Files 100

Renaming and Moving Files with mv 102

Removing Files and Directories 103

Working with Links 105

Compressing and Archiving Files 107

Files on Other Operating Systems 110

5 Finding Files and Information 111

The Oddly Named grep Command 111

Useful grep Options 112

Working with Regular Expressions 114

Finding Files with locate 118

Building the locate Database 118

Using locate 119

Using find to Explore Your Filesystem 120

Matching by File Size 121

Exploring find Permission Strings 122

Using find to Identify Recently Changed Files 124

find’s Faithful Sidekick: xargs 125

Further Refinements to find 127

Shining a Light on Spotlight 128

Listing Spotlight Metadata with mdls 128

Finding Files with mdfind 132

Making Spotlight Useful 133

6 Redirecting I/O 135

Standard Input and Standard Output 135

Putting Text in a File 137

Pipes and Filters 141

wc 142

tr 143

grep 144

Table of Contents | v

head and tail 145

sort 145

uniq 147

Piping Output to a Pager 147

Printing 149

The Unix Way 149

7 Multitasking 153

Running a Command in the Background 154

Checking on a Process 155

ps 155

top 157

Other Options for Monitoring Processes 160

Canceling a Process 162

kill 162

killall 163

Launching GUI Applications 164

open 165

Useful Starting Options for Use with open 166

Making open More Useful 167

8 Taking Unix Online 169

Remote Logins 169

Web Access 173

Remote Access to Other Unix Systems 173

Transferring Files 176

scp and rcp 176

FTP 177

Easy Shortcuts with New Remote Connection 183

9 Of Windows and X11 185

X11 186

Using X11 188

Differences Between OS X and X11 190

Customizing X11 191

GIMP, the X11 Graphics Editor 193

10 Where to Go from Here 195

Documentation 195

The Terminal’s Help Menu 195

The man Command 196

Documentation on the Internet 199

vi | Table of Contents

Books 200

Customizing Your Unix Experience 200

Shell Aliases and Functions 200

Programming 201

Perl, Python, and Ruby 202

C and C++ 203

Index 205

Table of Contents | vii

It’s been a long time since we went through the dramatic transition from Mac OS 9 to the more complicated and graphically rich world of OS X Many of you reading this have never known a Mac interface that wasn’t actually OS X (pronounce that “oh-ess ten” to sound cool) The biggest change when Apple switched operating systems was that every machine then gained multitasking and multiuser capabilities

What you might not have realized, however, is that it was the underlying operating system itself that changed in the update to OS X, and that you now have a tremendously powerful OS that can run thousands of open source applications downloaded free from the Net, along with a command-line interface that makes even the most complex tasks

a breeze

If you want to learn the key phrases, beneath OS X lies an operating system called Unix (pronounced “you-nicks”): specifically, UC Berkeley’s BSD Unix and the Mach kernel,

a multiuser, multitasking operating system Being multiuser means OS X allows multiple

users to share the same system, each with their own settings, preferences, and separate

area in the filesystems, secured from other users’ prying eyes Being multitasking means

OS X can easily run many different applications at the same time, and if one of those applications crashes or hangs, the entire system doesn’t need to be rebooted Instead, you just force quit the application that’s causing the “Spinning Beach Ball of Death” (you know, when the mouse pointer turns into a spinning color wheel that just won’t stop rotating) and either relaunch it or proceed with your work in other apps

ix

The fact that OS X has Unix under the hood doesn’t matter to users who simply want

to use its slick graphical interface to run their applications or manage their files But it opens up a world of possibilities for users who want to dig a little deeper The Unix

command-line interface, which is accessible through the Terminal application (/Appli­ cations/Utilities), provides an enormous amount of power for intermediate and ad­

vanced users What’s more, once you’ve learned to use Unix in OS X, you’ll also be able

to use the command line in other versions of Unix, such as FreeBSD (from which OS X derives its Unix core) or even the hugely popular Linux

This book is designed to teach Mac users the basics of Unix You’ll learn how to use the

command line (which Unix users refer to as the shell) and the filesystem, as well as some

of Unix’s most useful commands I’ll also give you a tour of some useful Unix commands that Apple’s team have written and include with every Mac system—utilities that let you really gain control over your system Unix is a complex and powerful system, so I can only scratch the surface, but I’ll also tell you how to deepen your Unix knowledge once you’re ready for more

Who This Book Is For

This book is for savvy Mac users who are comfortable in their current world (the Finder and other GUI applications) but also want to learn more about the “Power of Unix” that Apple keeps talking about Here, you’ll learn all the basic commands you need to get started with Unix Rather than weighing you down with lots of details, I want to help you get comfortable in the Unix environment as soon as possible So, I cover each com­mand’s most useful features instead of describing all its options in detail And let me tell you, Unix has thousands of commands with millions of options It’s very powerful! But fortunately, it’s just as powerful and helpful even if you just focus on a core subset and gradually learn more as you need additional power and capabilities

Who This Book Isn’t For

If you’re seeking a book that talks about how to build Mac software applications, this isn’t it (although it’s quite helpful for developers to have a firm grasp of Unix essentials, because you never know when you’re going to need them) And if you’re a complete beginner and are occasionally stymied by where the second mouse button has gone, you might be better off putting this book on the shelf until you’re more comfortable with your Macintosh

Finally, if you live and breathe Unix every day, this book is probably too basic for you

I also don’t cover either Unix system administration or Mac system administration from

the command line For example, if you already know what a PID is and how to kill a

program, this book is probably beneath your skill level But if you don’t know what those terms mean, or if you’re somewhere in between, you’ve found the right book!

x | Preface

A Brief History of Unix

The Macintosh started out with a single-tasking operating system that allowed simple switching between applications through an application called the MultiFinder More recent versions of the Mac OS have supported multiple applications running simulta­neously, but it wasn’t until the landmark release of OS X that true multitasking arrived

in the Macintosh world With OS X, Macintosh applications run in separate memory areas; the Mac is a true multiuser system that also includes proper file-level security

To accomplish these improvements, OS X made the jump from a proprietary underlying operating environment to Unix OS X is built on top of Darwin, a version of Unix based

on BSD 4.4 Lite, FreeBSD, NetBSD, and the Mach microkernel

Unix itself was invented more than 40 years ago for scientific and professional users who wanted a very powerful and flexible OS It has evolved since then through a remarkably circuitous path, with stops at Bell Telephone Labs, UC Berkeley, and research centers in Australia and Europe, and also received some funding from the US Department of Defense Advanced Research Projects Agency (DARPA) Because Unix was designed by experts for experts (or “geeks,” if you prefer), it can be a bit overwhelming at first But after you get the basics (from this book!), you’ll start to appreciate some of the reasons

to use Unix For example:

• It comes with a huge number of powerful programs, and you can get many others for free on the Internet (The Fink project, available from SourceForge—http://

fink.sourceforge.net—brings many open source packages to OS X.) You can thus do

much more at a much lower cost

• Unix is pretty much the same, regardless of whether you’re using it on OS X, FreeBSD, or Linux, or even in tiny embedded systems or on a giant supercomputer After you read this book, you’ll not only know how to harness the power of Unix, but you’ll also be ready to use many other kinds of Unix-based computers without having to learn new commands for each one

Versions of Unix

There are several versions of Unix Some past and present commercial versions include Solaris, AIX, and HP/UX Freely available versions include Linux, NetBSD, OpenBSD, and FreeBSD Darwin, the free Unix version underneath OS X, was built by grafting an advanced version called Mach onto BSD, with a light sprinkling of Apple magic for the Aqua interface

Although GUIs and advanced features differ among Unix systems, you should be able

to use much of what you learn from this introductory handbook on any system Don’t

Preface | xi

worry too much about what’s from what version of Unix Just as English borrows words from French, German, Japanese, Italian, and even Hebrew, OS X’s Unix borrows com­mands from many different versions of Unix—and you can use them all without paying attention to their origins.

From time to time, I explain features of Unix on other systems Knowing the differences can help you if you ever want to use another type of Unix system When I write “Unix”

in this book, I mean “Unix and its versions,” unless I specifically mention a particular version

Interfaces to Unix

Unix can be used as it was originally designed: on typewriter-like terminals, from a prompt on a command line Most versions of Unix also work with window systems, or graphical user interfaces (GUIs) These allow each user to have a single screen with multiple windows—including “terminal” windows that act like the original Unix interface

OS X includes a simple terminal application for accessing the command-line level of the system That application is called the Terminal and is closely examined in Chapter 2.While you can use your Mac quite efficiently without issuing commands in the Terminal, that’s where we’ll spend all of our time in this book Why?

• Every modern Macintosh has a command-line interface If you know how to use the command line, you’ll always be a power user

• If you become a more advanced Unix user, you’ll find that the command line is actually much more flexible than the graphical Mac interface Unix programs are designed to be used together from the command line—as “building blocks”—in an almost infinite number of combinations, to do an infinite number of tasks No window system I’ve seen has this tremendous power

• You can launch and close any Mac program from the command line

• Once you learn to use the command line, you can use those same techniques to

write scripts These little (or big!) programs automate jobs you’d have to do manually

and repetitively with a window system (unless you understand how to program a window system, which is usually a much harder job) See Chapter 10 for a brief introduction to scripting

• In general, text-based interfaces are much easier than graphical computing envi­ronments for visually impaired users

I’m not saying that the command-line interface is right for every situation For instance, using the Web—with its graphics and links—is usually easier with a GUI web browser

xii | Preface

within OS X But the command line is the fundamental way to use Unix Understanding

it will let you work on any Unix system, with or without windows A great resource for general OS X information (the GUI you’re probably used to) is OS X Mountain Lion:

The Missing Manual, by David Pogue (Pogue Press/O’Reilly).

How This Book Is Organized

This book will help you learn Unix on your Mac fast It is organized in a way that gets you started quickly and then expands your Unix horizons, chapter by chapter, until you’re comfortable with the command line and with X11-based open source applications and able to push further into the world of Unix Specific commands, for example, may

be previewed in earlier chapters and then explained in detail in later chapters (with cross references so you don’t get lost) Here’s how it’s all laid out:

Chapter 1, Why Use Unix?

Graphical interfaces are useful, but when it’s time to become a power user—really forcing your Mac to do exactly what you want, when you want it—nothing beats the power and capability of the Unix command line You’ll see exactly why that’s the case in this first chapter

Chapter 2, Using the Terminal

It’s not the sexiest application included with OS X, but the Terminal, found in the / Applications/Utilities folder, opens up the world of Unix on your Mac and lets you

peek inside the inner workings This chapter explains how to best use it and cus­tomize it for your own requirements

Chapter 3, Exploring the Filesystem

Once you start using Unix, you’ll be amazed at how many more files and directories are on your Mac—information that’s hidden from the graphical interface user This chapter takes you on a journey through your Mac’s filesystem, showing you how to list files, change directories, and explore the hidden nooks and crannies of Mountain Lion

Chapter 4, File Management

Now that you can move around in your filesystem, it’s time to learn how to look into individual files; copy or move files around; and even create, delete, and rename directories This is your first introduction to some of the most powerful Unix com­

mands, too, including the text-based vi editor.

Chapter 5, Finding Files and Information

If you’ve ever looked for a file with the Finder or Spotlight, you know that some types of searches are almost impossible Looking for a file that you created exactly

30 days ago? Searching for that file with the Finder will prove to be an exercise in

futility But that’s exactly the kind of search you can do with Unix’s find, locate, and grep commands, as well as Spotlight’s command-line utilities.

Preface | xiii

Chapter 6, Redirecting I/O

One of the most powerful elements of the Unix command line is that you can easily combine multiple commands to create new and unique “super-commands” that perform exactly the task you seek You’ll learn exactly how you can save a command’s output to a file, use the content of files as the input to Unix commands, and even hook multiple commands together so that the output of one is the input of the next You’ll see that Unix is phenomenally powerful, and easy, too!

Chapter 7, Multitasking

As mentioned earlier, Unix is a multitasking operating system that allows you to

have lots of applications running at the same time In this chapter, you’ll see how you can manage these multiple tasks, stop programs, restart them, and modify how they work, all from the Unix command line

Chapter 8, Taking Unix Online

Much of the foundation of the Internet was created on Unix systems, and it’s no surprise that you can access remote servers, surf the Web, and interact with remote filesystems, all directly from the command line If you’ve always wanted more power when interacting with remote sites, this chapter dramatically expands your hori­zons

Chapter 9, Of Windows and X11

The graphical interface in OS X is the best in the industry Elegant and intuitive, it’s

a pleasure to use But it turns out that there’s another, Unix-based graphical interface lurking in your Mac system, called the X Window System, or X11 for short This chapter shows you how to install X11 and gives you a quick tour of some of the very best X11 applications available for free on the Internet

Chapter 10, Where to Go from Here

With all its commands and command-line combinations, and the addition of thou­sands of open source utilities free for the downloading, you can spend years learning how to best take advantage of the Unix environment In this final chapter, I offer you some directions for your further travels, including recommendations for fa­vorite books, websites, and similar resources

Conventions Used in This Book

The following typographical conventions are used in this book:

Plain text

Indicates menu titles, menu options, menu buttons, and keyboard accelerators (such as Alt and Control)

xiv | Preface

Constant width bold

Shows commands or other text that should be typed literally by the user

Constant width italic

Shows text that should be replaced with user-supplied values or by values deter­mined by context

Menus/navigation

Menus and their options are referred to in the text as File→Open, Edit→Copy, etc Arrows are also used to signify a navigation path when using window options; for example, System Preferences→Screen Effects→Activation means you would launch System Preferences, click on the icon for the Screen Effects preferences panel, and select the Activation pane within that panel

Menu symbols

When looking at the menus for any application, you will see some symbols associ­ated with keyboard shortcuts for a particular command For example, to open a document in Microsoft Word, you could go to the File menu and select Open (File→Open), or you could issue the keyboard shortcut ⌘-O

Figure P-1 shows the symbols used in the various menus to denote a keyboard shortcut

Rarely will you see the Control symbol used as a menu command option; it’s more often used in association with mouse clicks to emulate a right-click on a two-button mouse or for working with the bash shell.

Preface | xv

Figure P-1 Keyboard accelerators for issuing commands

$,#

The dollar sign ($) is used in some examples to show the user prompt for the bash shell; the hash mark (#) is the prompt for the root user.

This icon signifies a tip, suggestion, or general note

This icon indicates a warning or caution

Using Code Examples

This book is here to help you get your job done In general, you may use the code in this book in your programs and documentation You do not need to contact us for permis­sion unless you’re reproducing a significant portion of the code For example, writing a program that uses several chunks of code from this book does not require permission Selling or distributing a CD-ROM of examples from O’Reilly books does require per­mission Answering a question by citing this book and quoting example code does not require permission Incorporating a significant amount of example code from this book into your product’s documentation does require permission

We appreciate, but do not require, attribution An attribution usually includes the title,

author, publisher, and ISBN For example: “Learning Unix for OS X, by Dave Taylor

Copyright 2012 Dave Taylor, 978-1-4493-3231-0.”

If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at permissions@oreilly.com

xvi | Preface

A Word on OS X Versus Mac OS X

Apple has always referred to the latest generation of the Mac operating system as “Mac

OS X,” but with the introduction of Mountain Lion and the path toward a unified user experience across computers and more portable devices like the Apple iPad and Apple iPhone, the operating system has been rebranded simply “OS X.” We will endeavor to use this new name for the system throughout the book, unless it makes more sense in context to use the older version of the OS name

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The Evolution of This Book

This book is loosely based on the popular O’Reilly title Learning the Unix Operating

System, by Jerry Peek, Grace Todino, and John Strang (currently in its fifth edition)

There are lots of differences in this book to meet the needs of OS X users, but the fundamental layout and explanations are the same The Mountain Lion edition is the fifth OS X custom edition of this title As OS X keeps getting better, so does this little book

Acknowledgments

I’d like to acknowledge the work of Meghan Blanchette and Brian Jepson at O’Reilly Without their work constantly explaining the nuances of the version tracking system we’ve used, I would have given up and made a really long YouTube video about the command line instead I would also like to express my gratitude to Dave Kitabjian, who did an extraordinary job as our tech editor, helping uncover the many obsolete portions

of this manuscript as we updated a seven-year-old book for Mountain Lion Thanks also

to Christian Crumlish for his early back-room assistance, and to Tim O’Reilly for the

opportunity to help revise the popular Learning the Unix Operating System book for the

exciting world of OS X, all those years ago

xviii | Preface

CHAPTER 1 Why Use Unix?

Why would any sane person want to type in a bunch of funny-looking Unix commands

when you can just use the mouse? After all, OS X has one of—if not the—best looking

user interfaces out there, so what would compel you, a Mac user through and through,

to use the Unix command line? That’s a tough sell, but you can boil it down to just one word: power.

Lying underneath the OS X interface is a powerful Unix system, ready to leap into action

at a moment’s notice All you have to do is command Unix to take action One of the

greatest pleasures of using Unix within OS X is that you get the benefit of a truly won­derful graphical environment and the underlying power of the Unix command line There’s no denying it’s a match made in heaven Even Apple promotes OS X with the tagline, “The world’s most advanced desktop operating system.”

This chapter sets the stage for the rest of the book, answering the question: “Why use Unix when you have a perfectly good Mac graphical interface?” It’s an important ques­tion, but I think that if you give it a try, you’ll agree that joining the Unix world is really like learning you have a completely separate, and even more powerful, operating system lurking in your machine

The Power of Unix

It’s quite reasonable to question why you should have to remember commands and type them in If you’re a long-time Mac user who is familiar and happy with the capabilities

and logic of the Aqua interface, you might need some convincing that Unix is your friend Here’s why: dipping into the primarily text-based Unix tools on your OS X system

gives you more power and control over both your computer and your computing envi­ronment There are other reasons too, including:

1

• There are thousands of open source and otherwise freely downloadable Unix-based applications Can’t afford Adobe Photoshop but still want a powerful graphics ed­itor? The GNU Image Manipulation Program (GIMP) offers a viable solution (see Chapter 9).

• Want to search for files by when they were created, or by whom? Difficult in the Finder or Spotlight, but it’s a breeze with Unix (see Chapter 5)

• How about managing your files and file archives in an automated fashion? Tricky

to set up with the GUI tools, but in Unix, you can set up a cron job to handle this

at night while you sleep

Fundamentally, Unix is all about power and control As an example, consider the dif­

ference between using Force Quit from the Apple menu and the Unix programs ps and kill While Force Quit is more attractive, as shown in Figure 1-1, notice that it lists only graphical applications

Figure 1-1 Force Quit doesn’t show all running applications

By contrast, the ps (process status) command used from within the Terminal application (/Applications/Utilities/Terminal) shows a complete and full list of every application,

utility, and system process running on your Mac, as shown here:

1583 ?? 0:24.08 Google Chrome Helper

Okay, now let’s go back and look at the output from running the ps -acx command First off, you’ll see that we added some options (or flags or switches) to the ps command; the options are the -acx bit These options tell ps to display all of the programs and processes

being run by all of the users (including you and the system, itself) on the system When

the Terminal displays the results of the ps -acx command, you’ll see that it adds a line

of “headers” to the output:

listed above (diskarbitrationd—the final “d” stands for daemon, an always-running

system-level task)

TIME

Tells you the amount of time it took to run that particular process, or how long that process has been running, in minutes and seconds For example, the 0:00.24 you see in the output above means that it took, roughly, a quarter of a second for the

diskarbitrationd process to start and run.

The Power of Unix | 3

Great! So now you know what all that means, but you still don’t know how this relates

to Force Quit, right? Well, be patient, we’re getting there

Once you know a process’s PID number, you can then issue the Unix kill command to,

well, kill that process For example, let’s say that Microsoft Word decides to lock up on you and you’re stuck with the Spinning Beach Ball of Death (SBBoD) syndrome After

you finish screaming, you need to kill Microsoft Word, but in order to do so, you first need its process number For this, we’ll add the grep command, which is basically a Unix

search tool that you use to search for words or numbers in files, or in this case, the output

of a command:

$ ps -ax | grep Word

1634 ?? 0:02.50 /Applications/Microsoft Office 2011/Microsoft

Word.app/Contents/MacOS/Microsoft Word -psn_0_766139

1645 ttys002 0:00.00 grep Word

This tells us that Microsoft Word’s PID is 1634, as noted by the first number in the

command output Now all you need to do to kill Word is issue the following command:

$ kill 1634

After typing that and hitting the Return key (an activity known as “entering a com­mand”), Microsoft Word promptly quits, closing all its windows It won’t save anything you’ve done, since your last save, but since Word was locked in a deep freeze you wouldn’t have been able to save your changes anyway, right? And if you had used the Force Quit window, you wouldn’t have been able to save changes there, either

Batch Renames and Extracting File Lists

Here’s another example Suppose you just received a data CD from a client with hundreds

of files in a single folder Now let’s say that you only need those files that have the

sequence -nt- or -dt- as part of their filenames, and that you want to copy them from

the CD to your home directory Within the Finder, you’d be doomed to going through the list manually, a tedious and error-prone process But on the Unix command line, this becomes a breeze:

$ cd /Volumes/MyCDROM

$ cp *-dt-* *-nt-* ~

The first command, cd /Volumes/MyCDROM, takes you to the Volumes directory, which

is where the CD (named MyCDROM) is actually mounted on your Mac’s filesystem The second command, cp *-dt-* *-nt-* ~, breaks down as follows:

4 | Chapter 1: Why Use Unix?

Fast, easy, and doable by any and all OS X users.

There are a million reasons why it’s helpful to know Unix as an OS X power user, and you’ll see them demonstrated time and again throughout this book

Finding Hidden Files

You might not realize it if you only work in the Finder, but your system has thousands

of additional files and directories that are hidden from view, but easily found on the

command line These hidden files are known in the Unix world as dot files, because each

file or directory has a period (.) as the first character of its name For example, in your

home directory you probably have a file called profile that contains specific instructions

on how you want your command shell set up when it’s launched But when you view your home folder in the Finder, this file is hidden, as shown in Figure 1-2 Instead, all

you see are the default set of folders (Desktop, Documents, Library, Movies, Music, Pic­ tures, Public, and Sites) and a file called myopen.

To view the dot files in the Terminal, type the file listing command (ls), along with its -a option (for list all, which shows the hidden dot files) Suddenly you’ll see that there

are lots more files in that directory:

$ ls -a

./ .dropbox/ vuescanrc Pictures/

/ dvdcss/ Desktop/ Presentations/

.CFUserTextEncoding lesshst Documents/ Public/

.DS_Store nchsoftware/ Downloads/ Sites/

.Trash/ profile Dropbox/ bin/

.android/ ssh/ Library/

.bash_history .subversion/ Movies/

.cups/ .viminfo Music/

The Power of Unix | 5

Figure 1-2 The Finder doesn’t show hidden files that you can see in the Terminal with standard Unix commands

Personally, though I don’t always need the power, I like knowing that I can get to, view, and even edit every file on my computer if I need to All I need to do is launch the Terminal application (which I actually have permanently available on my Dock, so it’s always just one click away), type in a few simple commands, and I’m on my way

Folders or Directories?

If you’re new to the whole Unix thing, you’re going to need to learn Unix-speak In the graphical world, such as with OS X or Windows, you’re used to working with a graphical user interface (GUI) that lets you see everything visually When you create a new file, it gets stored in a folder of some sort, even if you save the file to your Desktop (which is,

in its own right, a folder)

But in Unix-land, folders are referred to as directories That’s right, folders and directories

are one and the same It’s an odd sort of translation, but when Unix was first developed, there was no GUI; all you had was a text-based terminal to type into, and you were darn happy to have that, especially as you were walking 10 miles uphill in the snow to and from school each day But I digress!

Directories were set up as part of the hard drive’s filesystem, or the structure in which

directories and files are stored on the system And the way you get to a folder (er, di­

rectory) in Unix is to enter its file path, using forward slashes between the directory

names For example, the file path to your home directory (again, think folder) is actually:

/Users/your_name

6 | Chapter 1: Why Use Unix?

where your_name would be replaced by your short username Or use the power user shortcut ~, as shown earlier!

At the very top of your Mac’s filesystem, you have the root directory, denoted with a

single forward slash (/) As noted in the example above, to specify a particular directory

or file all you need to do is place the path after this leading slash

This takes a little getting used to, but once you get the hang of entering Unix file paths, you’ll find that it’s actually a faster way to get around (particularly if you can type faster than it takes you to move the mouse around in the graphical world)

Just remember: folders are directories, and when working on the Unix side of your Mac, we’ll refer to folders as directories throughout the book

Thousands of Free Applications

This should appeal to anyone who is a part of the Macintosh community: by warming

up to Unix and its command line, you are joining the much-lauded free software move­

ment, since OS X is based on a free, open source Unix operating system called Dar­ win What’s excellent is that there are thousands of different applications available for

open source operating systems, including design, development, scientific, and business applications that compare quite favorably to expensive commercial alternatives And don’t make the mistake of assuming that all open source applications are command-line tools and utilities! Some of the very best applications, like the GIMP graphics editor (http://www.gimp.org) and the NeoOffice suite (http://www.neooffice.org), are designed

to work either within the X Window System (also known as X11), a standard Unix graphical interface that Apple includes with your OS X system, or directly in OS X’s Aqua GUI environment

Power Internet Connections

If you’re someone who uses the Internet daily, you already know that there are a bunch

of useful Mac OS X applications available to help you be more efficient Unfortunately, lots of them seem to have a price tag attached—even a simple FTP program like Fetch (http://www.fetchsoftworks.com) But why spend $29 on an application when you can

use OS X’s built-in ftp command-line utility for free?

For example, if you wanted to download the cover image for this book from O’Reilly’s

website, you could use the following commands (as noted in bold type):

$ ftp ftp.oreilly.com

Connected to ftp.oreilly.com.

220 ProFTPD 1.3.1rc2 Server (ftp.oreilly.com) [208.201.239.51]

Name (ftp.oreilly.com:taylor): anonymous

331 Anonymous login ok, send your complete email address as your password

Password:

230-Welcome to the O'Reilly Media, Inc FTP Archive.

Thousands of Free Applications | 7

Local date and time: Mon Apr 23 23:04:14 2012

> Hello 71.237.2.63

> There are 2 users out of 100 allowed in your usage class

Check us out on the web at http://oreilly.com

230 Anonymous access granted, restrictions apply

Remote system type is UNIX.

Using binary mode to transfer files.

ftp> cd /pub/graphics/book-covers/low-res

250 CWD command successful

ftp> get 0596009151.gif

local: 0596009151.gif remote: 0596009151.gif

229 Entering Extended Passive Mode (|||62244|)

150 Opening BINARY mode data connection for 0596009151.gif (267646 bytes)

That downloads the image file for the cover of this book to your Mac, which is nice, but

what if you want to look at it? Sure, you could go to the Finder, find the file, and then

double-click on the file’s icon to open it in Preview, but that’s a lot of work Instead, with

a little help from Unix, you can just type in the following command:

$ open 0596009151.gif

$

The open command, which is special to OS X, examines the file it’s supposed to open (0596009151.gif), detects which application should open it by default (something you

can see in a file’s Get Info window), and then opens the file in Preview—all in a fraction

of a second! See how much time Unix just saved you (not to mention the $29!)?From logging into your Mac from remote locations to transferring files from your system

to a server using an encrypted connection, OS X’s Unix command line is quite powerful But don’t take my word for it—Chapter 8 takes you on a detailed tour of command-line Internet utilities

Commands Included with Unix

While this book covers only about 50 of the most basic Unix commands, there are over

a thousand Unix commands included with OS X—and you can’t see most of them without accessing the command line From sophisticated software development envi­ronments to web browsers, file transfer utilities to encryption and compression utilities, almost everything you can do in the Aqua interface—and more—can be done with a few carefully chosen Unix commands

8 | Chapter 1: Why Use Unix?

Displaying All Unix Commands

To quickly see all of the binary executables—Unix programs—on your system, open the Terminal, hold down the Shift key, and press Esc-?, or press Control-X followed by Shift-1 (using Shift-1 to get an exclamation mark)

Before the commands are displayed in the Terminal, however, you’ll first be prompted (asked) to make a choice:

$

Display all 1718 possibilities? (y or n)

If you press the n key on your keyboard, you’ll be taken back to a command prompt and nothing else will happen However, if you press the y key, you’ll see a multicolumn list

of Unix commands stream past in the Terminal window At the bottom of the screen, you’ll see:

More This lets you know that there’s more to display If you hit the space bar, the next “page”

of commands scrolls into view Keep pressing the space bar to view the entire list of commands; or, if you’re getting tired of that, just hit “q” to quit the output and go back

to the command prompt

If you’re a software developer or are just curious about programming, for example, you’ll want to install the optional Xcode Tools, available as a free download from the Apple Developer’s Site The Xcode Tools give you a full, professional-grade software develop­ment environment that lets you develop new applications in Objective-C, C, or C++ Pretty nice for something free from Apple, eh?

The 10 Most Common Unix Commands

If you want to just jump in and try things out, here are the 10 most common commands, with a very short summary of what each does:

Removes a file, set of files, or folder(s) full of files

Commands Included with Unix | 9

Use the rm command with caution; there’s no “Trash” where things are

moved to Once you’ve used rm to delete something, it’s gone forever.

Accesses OS X’s built-in documentation for the Unix commands To read the man

page for the ls command, for example, type in man ls.

less filename

Displays a long text file, one screen at a time Pressing the space bar gets the next page when you’re ready, and pressing Q at any time quits the program and returns you to the command prompt

grep pattern filename(s)

Searches for the specified pattern across as many files as you desire—a fast way to find that email message you sent to Uncle Linder, for example

top

Shows you which applications and processes are running on your system, including those that the Finder’s Force Quit window ordinarily hides

A Simple Guided (Unix) Tour

Enough talking about what Unix can do; it’s time to flex your fingers, open up your Mac, and try a few commands so you can get a sense of how it all works!

The first step is to launch the Terminal application, through which you’ll interact with

the command shell Terminal is tucked into the Utilities folder within your Applica­ tions folder.

Since you’ll be using the Terminal application throughout this book (and hopefully in the future, as you grow more comfortable with Unix), you should drag the Terminal’s icon to the Dock so it’s always at the ready Or, if the Terminal’s already running, you can Control-click on its icon in the Dock and select Options→Keep in Dock, as shown

in Figure 1-3

10 | Chapter 1: Why Use Unix?

Figure 1-3 Control-click the Terminal’s Dock icon, and select “Keep in Dock” from the Options menu so it will always be there when you need it

Throughout the following examples, type in the commands you see in bold, pressing

the Return key after each one (again, this is known as “entering a command” in speak) Preceding each command, I’ve included some comments to let you know what you’re about to do

Unix-Without any arguments, the cd command moves you to your home directory:

$ cd

The pwd (present working directory) command shows you the path for the directory

you’re currently in:

$ pwd

/Users/taylor

Use the ls command to list the files in your home directory; compare this listing with

the picture of the Finder window shown in Figure 1-2 If you omit the -a option, all the

hidden dot files stay hidden in this directory:

$ ls

Desktop Dropbox Music Public

Documents Library Pictures Sites

Downloads Movies Presentations bin

Now let’s change directories to your Library folder:

$ cd Library

A Simple Guided (Unix) Tour | 11

Use the ls command again to see what’s inside (there’s very little here you’ll need to mess

with):

$ ls

Accounts FontCollections PreferencePanes

Address Book Plug-Ins Fonts Preferences

Application Support Fonts Disabled Printers

Assistants Frameworks PubSub

Audio Google Safari

Automator Icons Saved Application State

Autosave Information Input Methods Screen Savers

Breakpad Internet Plug-Ins Services

Caches Keyboard Layouts Snapz Pro X

Calendars Keychains Sounds

ColorPickers LaunchAgents Spelling

Colors Logs StickiesDatabase

Compositions Mail SyncedPreferences

Containers Mail Downloads Voices

Cookies Messages WebKit

Developer Metadata Widgets

FIPLAB Mobile Documents disclabel

Favorites PDF Services iMovie

FileSync Parallels iTunes

Now let’s go back a directory For this, use the shortcut for moving up one directory

in the filesystem In this case, since you were in your Library folder (e.g., /Users/taylor/ Library, or just ~/Library), the following command moves you back to your home di­ rectory (as noted by the pwd command that follows):

$ cd

$ pwd

/Users/taylor

Finally, when it’s time to quit the Terminal, use the exit command rather than just quit­

ting the application with ⌘-Q:

a Mac user Ready? Let’s go!

12 | Chapter 1: Why Use Unix?

CHAPTER 2 Using the Terminal

With a typical Unix system, a staff person has to set up an account for you before you can use it With OS X, however, the operating system installation process automatically

creates a default user account The account is identified by your username, which is

usually a single word or an abbreviation Think of this account as your office—it’s your personal place in the Unix environment

When you log into your OS X system, you’re automatically logged into your Unix ac­count as well In fact, your Desktop and other customized features of your OS X envi­ronment have corresponding features in the Unix environment Your files and programs can be accessed either through the Finder or through a variety of Unix command-line utilities that you can use in OS X’s Terminal application

In this chapter, you’ll not only learn about the Terminal and how to customize it for your own needs, but you’ll also gain an understanding of the command-line nature of

OS X when accessed through the Terminal If you’re used to moving your mouse around and clicking on buttons, this might seem wonderfully—or awkwardly—retro, but as is

so often the case, the differences between the Finder and the Terminal are part of what makes the Terminal, and Unix, so remarkably powerful

Launching the Terminal

The way you use Unix on OS X is through an application known as the Terminal, or, to

Mac geeks, Terminal.app (pronounced “Terminal dot app”) Open a Finder window and look in Utilities, as shown in Figure 2-1 Double-click on “Terminal” and it will start up, presenting you with a dull, uninspiring white window with black text that says “Last login:” and a shell prompt

13

Figure 2-1 Finding Terminal in the Utilities folder

By default, the Terminal uses bash as its shell If you’d like to configure

it to use a different shell, you can do so by selecting Terminal→Prefer­

ences and specifying the shell to use I talk about that in “What Is a

Shell?” (page 19), later in this chapter

Most OS X applications you’ve run to this point probably have a pretty graphical inter­face and allow you to move the cursor around with your mouse or trackpad Move it over something you want to do, and you can simply click for the action to take place The Terminal is different, though: your mouse gets a rest for a while as you type in the commands on your keyboard, ending each line with a Return

Syntax of a Unix Command

Unix command lines can be simple, one-word entries, such as the date command They

can also be more complex; you may need to type more than the command or program

name The command can be the name of a Unix program (such as date), or it can be a command that’s built into the shell (such as exit) You probably don’t need to worry

about this!

A Unix command can have arguments An argument can be an option or a filename

The general format for a Unix command line is:

command option(s) filename(s)

14 | Chapter 2: Using the Terminal

There isn’t a single set of rules for writing Unix commands and arguments, but these general rules work in most cases:

• Enter commands in lowercase Unix is case-sensitive, so echo and ECHO are not

you’ll have to try it

Some commands also have options made from complete words or phrases and starting with two dashes, such as delete or confirm-delete When you enter a

command line, you can use this option style, the single-letter options (which each start with a single dash), or both

• The argument filename is the name of a file you want to use Most Unix programs

also accept multiple filenames, separated by spaces or specified with wildcards (see Chapter 4) If you don’t enter a filename correctly, you may get a response such as

“filename: no such file or directory” or “filename: cannot open.”

Some commands, such as who, have arguments that aren’t filenames.

• You must type spaces between commands, options, and filenames You’ll need to

“quote” filenames that contain spaces For more information, see Chapter 4

• Options come before filenames

• In a few cases, an option has another argument associated with it; type this special argument just after its option Most options don’t work this way, but you should know about them The sort command is an example of this feature: you can tell sort

to write the sorted text to a filename given after its -o option In the following example, sort reads the file sortme (given as an argument), and writes to the file sorted (given after the -o option):

$ sort -o sorted -n sortme

I also used the -n option in that example, but -n is a more standard option; it has nothing to do with the final argument (sortme) on that command line So, I also

could have written the command line this way:

$ sort -n -o sorted sortme

Don’t be too concerned about these special cases, though If a command needs an option like this, its documentation will say so

Launching the Terminal | 15

• Command lines can have other special characters, some of which you’ll see later in this book They can also include several separate commands For instance, you can write two or more commands on the same command line, each separated by a semicolon (;) Commands entered this way are executed one after another by the shell.

OS X has a lot of commands! Don’t try to memorize all of them In fact, you’ll probably need to know just a few commands and their options As time goes on, you’ll learn these commands and the best way to use them for your job

Let’s look at a sample command The ls program displays a list of files You can use it

with or without options and arguments If you enter:

information about a particular file by using its name as the second argument For ex­

ample, to find out about a file called chap1, enter:

$ ls -l chap1

Many Unix commands have more than one option For instance, ls has the -a (all) option

for listing hidden files You can use multiple options in either of these ways:

$ ls -a -l

$ ls -al

You must type one space between the command name and the dash that introduces the

options If you enter ls-al, the shell reports back with:

ls-al: command not found

Exercise: Entering a Few Commands

The best way to get used to the Terminal is to enter some commands To run a command, type the command and then press the Return key Remember that almost all Unix com­mands are typed in lowercase Try issuing the commands shown in Table 2-1 to see what results are produced in the Terminal

16 | Chapter 2: Using the Terminal

Table 2-1 Sample Unix commands to test out

Get today’s date. date

List logged-in users. who

Obtain more information about users. who -u, finger, or w

Find out who is at your terminal. who am i

Enter two commands in the same line. who am i;date

Mistype a command. woh

In this session, you’ve tried several simple commands and seen the results on the screen

Types of Commands

When you use a program, you’ll want to know how to control it How can you tell it what job you want done? Do you give instructions before the program starts, or after it’s started? There are several general ways to run programs on an OS X system, and it’s good to be aware of them:

Graphical programs

Some programs work only within the graphical window environment On OS X,

you can run these programs using the open command For instance, when you type

open -a Chess at a command prompt, the Chess application (/Applications)

launches and opens one or more windows on your screen The program has its own way to receive your input—through menus and buttons on its windows, for instance Although you can’t interact with these programs using traditional Unix utilities, OS

X includes the osascript utility, which lets you run AppleScript commands from the

Unix shell

Noninteractive Unix programs

You can run many Unix programs (though we generally call them “commands” when they’re being typed in) directly at a shell prompt These programs work within

a specific command window and you control them from the Unix command line—that is, by typing options and arguments at a shell prompt before you start the program After you start the program, wait for it to finish; you generally don’t in­teract with it

Interactive Unix programs

Some Unix programs that work in the Terminal window have commands of their own (If you’d like some examples, see Chapters 3 and 4.) These programs may accept options and arguments on their command lines but, once you start a pro­gram, it prints its own prompt and/or menus, and it understands its own commands

It also takes instructions from your keyboard that weren’t given on its command line

Launching the Terminal | 17

For instance, if you enter ftp at a shell prompt (refer back to the example in Chap­ter 1), you’ll see a new prompt from the ftp program At this prompt, you can enter

certain FTP commands for transferring files to and from remote systems When you

enter the special command quit to quit the ftp program (or you can use bye), ftp stops

prompting you for more input Once you quit FTP, you’re returned to the standard Unix shell prompt, where you can enter other Unix commands

Changing the Terminal’s Preferences

To change the Terminal’s preferences, go to Terminal→Preferences; this opens the com­plicated Preferences window, as shown in Figure 2-2

Figure 2-2 The Terminal Preferences window lets you configure the settings for your Terminal windows

At the top of the window, there’s a pop-up list that lets you select which options to configure: Startup, Settings, Window Groups, and Encodings The names suggest what each does, but let’s have a closer look anyway, particularly since some of these settings

definitely should be changed (in my view).

18 | Chapter 2: Using the Terminal

When you first open the Terminal Preferences, the Startup settings are displayed, as shown in Figure 2-2 This lets you manage the overall behavior of a window, including its color scheme (my default is “Ocean”), what shell you’d like to use, and even what happens when you open a specific tab

What Is a Shell?

A shell, at least in the Unix world, is the environment in which you work on the Unix side

of things To put this into context, when you’re using the Aqua user interface for OS X, you’re using OS X’s native “environment.” With Unix, however, everything is text-based, and the shell offers you an interface in which to issue commands, and to configure how your shell environment works and behaves

Shells also offer their own scripting language, which allow you to write mini-programs for mundane things, such as displaying a message to tell you to clean the cat box, or much larger tasks, such as backing up your computer With shell scripts, you’re basically using the shell’s environment to run Unix commands—or other shell scripts—to automate tasks and processes

If you want to learn more about the bash shell and how to program shell scripts with it,

look to the venerable Learning the bash Shell by Cameron Newham and Bill Rosenblatt (O’Reilly) Don’t let the age of this book fool you; it’s packed with lots of useful information that still applies to using bash under OS X And if you want to see what you can do with

shell scripts, I’d recommend picking up a copy of Wicked Cool Shell Scripts (No Starch

Press), authored by yours truly and still a timely and popular scripting reference

The choice of shells in OS X are: /bin/bash, /bin/csh, /bin/ksh, /bin/tcsh, /bin/zsh, and /bin/sh Unix fans will no doubt find a shell to their liking, but if you’re just learning, stick with bash (/bin/bash) and you’ll be able to follow every example in this book without

a hiccup

Settings

The Settings pane (shown in Figure 2-3) shows lots of different appearance options, including nice visual thumbnails of the many different predefined color schemes avail­able in the Terminal

The left side of the Settings window shows the different color profiles, but the right side

is where the action is It’s split into five sections: Text, Window, Shell, Keyboard, and Advanced

The text section is where you can specify what typeface you want to use: what size, what color, etc You can see all of the options in Figure 2-4

Launching the Terminal | 19

Figure 2-3 Terminal Preferences Settings pane

If you use a predefined profile, of course, you don’t have to tweak any of the color settings, but I know that some people can spend hours fiddling and tweaking to get it just so.The most interesting section of the Settings pane of the Preferences window is the Win­dow section, shown in Figure 2-3 Here, you can add useful information to the Terminal window, change the background of the Terminal window to a graphic or photo (though

I can’t imagine why you would!), and change the default window size The standard size

is 25 lines by 80 characters, but that’s just a historical artifact from the early neolithic era of computing Setting the size to 100 characters wide by 40 or 50 lines makes it considerably easier to work in the Terminal

One really nice thing that the Terminal does is save the textual information that scrolls off the top of the screen so you can scroll up and review what’s transpired earlier In the old days, once it was off the top, it was off, gone, kaput Now you can go back and review your command-line interaction from days or even weeks ago, depending on your avail­able memory You can also configure the size of the scrollback buffer in the Window section; by default, it is unlimited

20 | Chapter 2: Using the Terminal